Yasuhiro Kuramoto
Hiroshima University
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Biochimica et Biophysica Acta | 1983
Eiichi Kimura; Atsuko Yatsunami; Asuka Watanabe; Ryosuke Machida; Toru Koike; Haruto Fujioka; Yasuhiro Kuramoto; Mihoko Sumomogi; Kayo Kunimitsu; Aiko Yamashita
The superoxide dismutase (EC 1.15.1.1) activities of new series of macrocyclic complexes with copper(II) have been measured. Chemical modifications in macrocyclic ring size, donor atom, donor atom number, substituents on the macrocyclic skeletons, and length of bridges linking two macrocycles are shown to have profound effects on the superoxide dismutase activities of the metal complexes. The quantitative measurement by the standard xanthine-xanthine oxidase assay, which depends on the conversion of nitroblue tetrazolium to formazan, has been corroborated by a direct assay method using an oxygen electrode.
International Journal of Antimicrobial Agents | 2014
Daichi Kazamori; Hiroshi Aoi; Kaori Sugimoto; Taichi Ueshima; Hirotaka Amano; Kenji Itoh; Yasuhiro Kuramoto; Akira Yazaki
The aim of this study was to examine the in vitro antibacterial activity of WQ-3810, a new fluoroquinolone, against clinically relevant pathogens such as Acinetobacter baumannii, Escherichia coli and Streptococcus pneumoniae, including multidrug-resistant (MDR) and fluoroquinolone-resistant (FQR) isolates, compared with those of ciprofloxacin, levofloxacin, moxifloxacin and gemifloxacin. WQ-3810 demonstrated the most potent activity against the antimicrobial-resistant pathogens tested. Against A. baumannii, including MDR isolates, the potency of WQ-3810 [minimum inhibitory concentration for 90% of the organisms (MIC(90))=1 mg/L] was more than eight-fold higher than that of ciprofloxacin (64 mg/L) and levofloxacin (8 mg/L). Against E. coli and S. pneumoniae, including FQR isolates, WQ-3810 (MIC(90)=4 mg/L and 0.06 mg/L, respectively) was also more active than ciprofloxacin (64 mg/L and 2 mg/L) and levofloxacin (32 mg/L and 2 mg/L). Furthermore, WQ-3810 was the most potent among the fluoroquinolones tested against meticillin-resistant Staphylococcus aureus (MRSA) and Neisseria gonorrhoeae, including FQR isolates. In particular, WQ-3810 demonstrated highly potent activity against FQR isolates of A. baumannii, E. coli and S. pneumoniae with amino acid mutation(s) in the quinolone resistance-determining region of DNA gyrase and/or topoisomerase IV, which are the target enzymes of fluoroquinolones. An enzyme inhibition study performed using FQR E. coli DNA gyrase suggested that the potent antibacterial activity of WQ-3810 against drug-resistant isolates partly results from the strong inhibition of the target enzymes. In conclusion, this study demonstrated that WQ-3810 exhibits extremely potent antibacterial activity over the existing fluoroquinolones, particularly against MDR and FQR pathogens.
Chemical & Pharmaceutical Bulletin | 2018
Tatsuya Hirano; Tomohiko Kinoshita; Daichi Kazamori; Satoshi Inoue; Kouji Nishimura; Asuka Sakurai; Kensuke Ohishi; Yasuhiro Kuramoto; Hirotaka Amano; Akira Yazaki
WFQ-101 with a unique N-1 substituent, 5-amino-4-fluoro-2-(hydroxymethyl)phenyl group, was selected as a lead compound through combination screening based on antimicrobial activity and the efflux index against quinolone-resistant (QR) Pseudomonas aeruginosa (P. aeruginosa). Through structural optimization, we identified WFQ-228 as a novel fluoroquinolone antibiotic candidate. WFQ-228 had potent and superior activity in comparison to levofloxacin (LVX) and ciprofloxacin (CIP) against clinical isolates of P. aeruginosa, Escherichia coli and Acinetobacter baumannii, including QR strains. Furthermore, WFQ-228 demonstrated the potential to overcome major mechanisms of drug resistance; its antimicrobial activity was less affected by both pump-mediated efflux and mutations of the quinolone resistance-determining region in P. aeruginosa compared with LVX and CIP. These results suggest that WFQ-228 is a promising candidate for further evaluation in the treatment of infections caused by QR Gram-negative pathogens.
Journal of Organic Chemistry | 1990
Eiichi Kimura; Yasuhiro Kuramoto; Tohru Koike; Haruto Fujioka; Mutsuo Kodama
Journal of Medicinal Chemistry | 2003
Yasuhiro Kuramoto; Yoshihiro Ohshita; Jiro Yoshida; Akira Yazaki; Motoo Shiro; Tohru Koike
Archive | 1996
Akira Yazaki; Yoshiko Niino; Yoshihiro Ohshita; Yuzo Hirao; Hirotaka Amano; Norihiro Hayashi; Yasuhiro Kuramoto
Archive | 2000
Koji Nishimura; Yasuhiro Kuramoto; Koichi Tamura; Yuzo Hirao; Hirotaka Amano; Mitsuhiko Osaki; Jiro Yoshida; Shizuka Aoki; Kenji Sato
Archive | 1991
Masaharu Yokomoto; Akira Yazaki; Norihiro Hayashi; Shunso Hatono; Satoshi Inoue; Yasuhiro Kuramoto
Archive | 1990
Yasuhiro Kuramoto; Masayasu Okuhira; Takashi Yatsunami
Archive | 1990
Takashi Yatsunami; Hitodshi Yamamoto; Yasuhiro Kuramoto; Norihiro Hayashi; Akira Yazaki; Satoshi Inoue; Shuichiro Noda; Hirotaka Amano